ALBERT

Description: The mutational landscape of grey zone lymphoma (GZL) has not yet been established and differences to related entities are largely unknown. Here, we studied coding sequence mutations of 50 EBV-negative GZL and 20 polymorphic EBV-positive DLBCL NOS (poly-EBV-L) in comparison to classical Hodgkin lymphoma (cHL), primary mediastinal large B cell lymphoma (PMBCL), and diffuse large B cell lymphoma (DLBCL). Exomes of 21 GZL and 7 poly-EBV-L cases along with paired normals were analyzed as a discovery cohort followed by targeted sequencing of 217 genes in an extension cohort of 29 GZL and 13 poly-EBV-L cases. GZL cases with thymic niche involvement (anterior mediastinal mass) displayed a mutation profile closely resembling cHL and PMBCL, with SOCS1 (45%), B2M (45%), TNFAIP3 (35%), GNA13 (35%), LRRN3 (32%) and NFKBIA (29%) being the most recurrently mutated genes. In contrast, GZL cases without thymic niche involvement (N=18) had a significantly distinct pattern, enriched in mutations related to apoptosis defects (TP53 (39%), BCL2 (28%), BIRC6 (22%)) and depleted in GNA13, XPO1or NFKB signaling pathway mutations (TNFAIP3, NFKBIE, IKBKB, NFKBIA). They also presented more BCL2/BCL6 rearrangements as opposed to thymic GZL. Poly-EBV-L cases presented a distinct mutational profile including STAT3 mutations and a significantly lower coding-mutation load in comparison to EBV-negative GZL. Our study highlights characteristic mutational patterns in GZL associated with presentation in the thymic niche suggesting a common cell of origin with disease evolution overlapping with related anterior mediastinal lymphomas.

Description: Introduction: Grey zone lymphoma (GZL), a B-cell lymphoma with features intermediate between large B-cell lymphoma (LBCL) and classical Hodgkin lymphoma (cHL), is a rare and poorly defined entity. To decipher its mutational landscape and discover new therapeutic targets, we performed exome sequencing of 31 GZL cases. Methods: GZL cases from the LYSA group (N=139) and BC Cancer (N=30) were centrally reviewed and classified as previously published (Sarkozy et al, Am J Surg Pathol 2019). Whole-exome sequencing was performed on 31 cases with available fresh frozen tissue, using laser micro-dissection (LMD, MMI technology) to enrich for tumor cells and obtain matching normal DNA from microenvironment cells. DNA was extracted (Agencourt® DNAdvance kit) and genomic libraries were constructed with the Ovation ultra-low kit (Nugen®). Exome capture was performed using Agilent SureSelectXT V6+UTR followed by paired-end sequencing (NextSeq®). Somatic nucleotide variants (SNVs) and indels were identified using VarScan, Strelka and Mutect. Parameters affecting the sensitivity and specificity of variant calling were optimized using 7 "gold standard" cases for which DNA from peripheral blood cells was additionally available. Possible oncogenic drivers were identified based on rate of recurrence, MutSigCV and literature review. Results: Among the 31 GZL cases, the median age was 41 y (14-83) with a sex ratio of 15M:16F; 21 cases had mediastinal involvement, including 15 within the thymic area; EBER in-situ hybridization (ISH) was positive in 8 cases. Seven (23%) cases were classified as group-0 (cHL morphology with 100% CD20 expression), 22 (71%) with an intermediate morphology as group-1 (N=9, cHL-like morphology) or group-2 (N=13, LBCL-like morphology) and 2 (6%) as group-3 (LBCL with 100% of CD30 expression). The mean coverage was 96X (42-203) for tumor samples. One case was excluded due to failure in the LMD process. Among the 30 cases, 6628 variants across 4826 genes were found, including 2903 coding mutations (325 indels and 2808 SNVs, mean of 104/sample, range: 15-678), 721 affecting the 5' UTR and 2774 the 3' UTR. A total of 152 genes were identified as being potential oncogenic drivers, with a mean of 11 mutated genes per case (range 2-36). The most recurrently mutated genes were SOCS1 (33%), B2M (23%), GNA13 (20%), LRRN3 (17%), and ZNF217, NCOR1, ITPKB, IRF2BP2, CSF2RB, and CSMD3 (13% each). The epigenetic SWI/SNF and transcription regulation pathway (including NCOR1/2, ARID1A, KMT2D, KMT2A) was affected in 73% of the cases, JAK/STAT in 70% and NF-kB in 19%. As assessed by CNVkit and GISTIC, the most recurrent gains/amplifications identified were in 9p24.1 (JAK2, CD274, PDCD2LG2; 69%) and 2p16.1 (REL, BCL11A; 62%), and losses in 11q14.3 (ATM; 48%) and 12q24.33 (NCOR2; 48%). Based on mutational signature analysis, individual base substitutions were linked to mutagenic processes, with the highest contributions associated with aging (29%) and defective DNA mismatch repair (27%); moreover, mutations attributable to AID/APOBEC activity (5%), were found to be significantly enriched in EBV- vs. EBV+ cases (p = 0.013). EBV+ cases had fewer total variants (mean 98 vs 258, p=0.08) and potential oncogenic variants (mean 7 vs 15, p=0.03) compared to EBV- cases. EBV+ cases also lacked mutations in the NF-kB pathway and MHC-class I components (B2M and HLA-B: 0% vs 43% in EBV-, p=0.06) but had mutations in STAT3, DHX58, ACTB and ATP13A4 (6/7 cases) not present in the 23 EBV- cases. LRRN3 and GNA13 mutations were significantly associated with thymic area involvement (40% vs 0%, p=0.01). Furthermore, fluorescence-ISH indicated that 20% (1/5) of EBV+ cases had a rearrangement in the CIITA locus (16p13.13) vs 53% (9/17) in EBV- cases. Patients with an intermediate morphology had more oncogenic variants than those in group 0 and 3 (mean of 15 vs 6 variants/case, p=0.01 affecting 12 vs 5 genes, p=0.004). Finally, NCOR1 (N=4) and NCOR2 (N=2) mutations were exclusively found in cases with intermediate morphology (23% vs 0% for those with group 0 or 3 morphology). Conclusion: These data suggest that GZL is a highly heterogenous disease harboring somatic driver events shared with PMBCL and HL. We also discovered novel gene mutations pointing to the importance of previously unrecognized pathways in the pathogenesis of GZL. The distinct mutational pattern in EBV+ GZL suggests divergent evolutionary trajectories. Disclosures Sarkozy: Takeda: Research Funding. Salles:Merck: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis, Servier, AbbVie, Karyopharm, Kite, MorphoSys: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Educational events; Autolus: Consultancy, Membership on an entity's Board of Directors or advisory committees; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Educational events; Epizyme: Consultancy, Honoraria; BMS: Honoraria; Amgen: Honoraria, Other: Educational events; Roche, Janssen, Gilead, Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Educational events. Savage:BMS, Merck, Novartis, Verastem, Abbvie, Servier, and Seattle Genetics: Consultancy, Honoraria; Seattle Genetics, Inc.: Consultancy, Honoraria, Research Funding. Scott:Celgene: Consultancy; Roche/Genentech: Research Funding; Janssen: Consultancy, Research Funding; NanoString: Patents & Royalties: Named inventor on a patent licensed to NanoSting [Institution], Research Funding. Steidl:Juno Therapeutics: Consultancy; Tioma: Research Funding; Roche: Consultancy; Bristol-Myers Squibb: Research Funding; Nanostring: Patents & Royalties: Filed patent on behalf of BC Cancer; Seattle Genetics: Consultancy; Bayer: Consultancy.

Description: Key Points An accumulation of alterations in epigenetic modifiers and genes in the JAK/STAT pathway likely drives BI-ALCL oncogenesis. Whole exome sequencing of a large series of BI-ALCL demonstrates recurrent mutations in epigenetic regulators.

Description: Introduction Among recently discovered B cell activators responsible for signaling events leading to B-cell activation and maturation, of particular interest are the Toll-like receptors (TLRs). TLR expression is heterogeneous and variable among B-cells. In addition, abnormal TLR levels/signaling may play an important role in the pathogenesis of lymphoma, particularly in splenic marginal zone lymphoma (SMZL), since TLR pathways are recurrently targeted by genetic changes in this lymphoma. Methods Frozen spleen tissue specimens from patients with SMZL (n=13) and splenic diffuse red pulp lymphoma with villous lymphocytes (SDRPL, n=5) were analyzed for the expression of TLR1 to TLR10 in comparison to control cases (traumatic spleen, n=7) using multi-parametric flow cytometry and quantitative mRNA Taqman assay. To identify the B-cell subset, the samples were also stained with anti-CD19 and anti-CD3. All cases were studied by morphological, immunological, cytogenetic and molecular analysis. Results The TLR profile obtained at protein level by flow cytometry was closely related to that obtained at mRNA level. The SMZL/SDRPL B-cells expressed all TLRs, but with variable levels of protein expression (low for TLR1, TLR2, TLR3, TLR8, TLR9, TLR10, and high for TLR4, TLR5, TLR6 and TLR7). On the other hand, distinct TLRs profiles were observed according lymphoma subtypes. The SDRPL cases showed indeed a significant TLR2 under-expression and TLR4/TLR7 over-expression in comparison to SMZL cases and control B-cells. SMZL cases exhibited a significant TLR4/TLR8 over-expression in comparison to control B-cells. These TLR profiles were not associated with specific cytogenetic features (presence of del7q or trisomy 3) and/or immunological profile (expression of the CD11c/CD27/isotype of immunoglobulin). But, in both entities, TLR4 expression was higher in cases with mutated IGHV than in cases with unmutated IGHV. The overexpression of TLR7 MyD88-dependent signaling molecules has been reported as pathogenic mechanism for autoimmune diseases; however no more autoimmune disease or circulating auto-antibodies were associated with SDRPL cases as compared to SMZL cases. As previously reported, all cases but one SMZL case presented unmutated MyD88 (L265P mutation), and MyD88 protein evaluated here by flow cytometry was similarly expressed in both entities. While TLR7 stimulation is known to induce CD38 expression, all SDRPL cases were CD38 negative; while in SMZL cases, higher TLR7 expression was observed in CD38 positive as compared to CD38-negative cases. This may suggest the existence of an abnormal TLR7 pathway in SDRPL as opposed to SMZL. Conclusion TLR profiling should allow a better understanding of the mechanisms involved in SMZL/SDRPL pathogenesis. Present data suggest an abnormal TLR pathway involving NF-kB and/or MyD88 in the SDRPL entities. Disclosures: No relevant conflicts of interest to declare.

Description: Background: BIA-ALCL has recently been recognized as a distinct entity among T cell lymphomas. In the French Lymphopath network which has registered almost 60 000 lymphomas since 2010, 50 cases of BIA-ALCL were identified so far. Little is known about the causes, and prognostic factors of this disease. Methods: since 2016, a WebEx national multidisciplinary meeting has been implemented by the French Cancer Agency in order to better define therapeutic strategies for newly diagnosed cases after histologic confirmation. In the same time, BIA-ALCL registry was funded by LYSA in order to collect ambispectively patient clinical data including reasons for breast implantation (breast augmentation, reconstruction), implant manufacturer, treatments and outcome. Results: Thirty nine BIA-ALCL have been analyzed so far. Median age was 61 years (range 29-82) at diagnosis. In 20 out of 39 patients (pts) (51.3%) the first implant followed a mastectomy for breast cancer. Twelve pts were implanted twice (33%) and thirteen pts (36%) 3 times or more. The median delay between first implant and BIA-ALCL diagnosis was 11.9 years (range 4-37), and median delay from last implant to diagnosis was 3.6 years (range 0-26). The two clinical presentations i.e. seroma (n = 26 - 67%) and breast tumor mass with or without seroma (n = 9 - 23%) were most often correlated with the two distinct histological subtypes (in situ or infiltrative). The majority of pts (76.9%) were stage IE (n=30; 77%), and nine (23%) pts were stage IV. One hundred and thirty five implants have been used for these 39 patients. Considering available informations regarding the type of implants, almost all patients had at least one silicone-filled (n=35) and at least one textured implant (n=31). No patient had only smooth implant. Implant removal with total capsulectomy was performed in 33 patients and 13 underwent chemotherapy based mostly on CHOP or CHOP-like chemotherapy regimens (n=11; 85%). After 24 months of median follow-up, 33 pts are alive and free of evolutive disease. Two patients have not been evaluated. Four pts have died, either from lymphoma progression alone (n=2), or associated with concomitant breast cancer (n=2). All had an infiltrative histology, 3 were stage IV and one had a localized bulky disease. All but one received systemic chemotherapy and one received palliative care only due to concomitant breast cancer. One of these patients early relapsed after a first complete remission. Conclusions: In situ BIA-ALCLs have an indolent clinical course and remain in complete remission mainly after implant removal. Infiltrative BIA-ALCLs have a more aggressive clinical course. It is therefore critical to perform a rigorous staging using multi-imaging modality including TEP at baseline. Multiple implants could favor the occurrence of BIA-ALCL. New insights into the biology of BIA-ALCL might translate into more targeted and effective therapies in refractory or relapsed patients. The modalities of breast monitoring and reconstruction remain open questions for those patients. Disclosures Le Bras: Amgen: Consultancy. Bachy:Roche: Research Funding; Celgene: Consultancy; Amgen: Honoraria; Takeda: Research Funding; Janssen: Honoraria; Gilead Sciences: Honoraria; Sandoz: Consultancy. Fornecker:Servier: Honoraria; Takeda: Honoraria. Traverse-Glehen:Takeda: Research Funding; Astra Zeneca: Other: Travel. Tilly:Astra-Zeneca: Membership on an entity's Board of Directors or advisory committees; Karyopharm: Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees; BMS: Honoraria; Celgene: Membership on an entity's Board of Directors or advisory committees. Xerri:Janssen: Other: Travel. Gaulard:Celgene: Research Funding; Roche: Honoraria; Takeda: Consultancy, Honoraria, Research Funding. Haioun:Takeda: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Gilead Sciences: Consultancy, Honoraria; Sciences: Consultancy, Honoraria; Roche: Consultancy, Honoraria; Celgene: Consultancy, Honoraria; Amgen: Consultancy, Honoraria.

Description: Key Points Cases of cHL may express TCA on the neoplastic cells. TCA-cHL have nodular sclerosis histology and lack T-cell genotype, with worse outcome compared with TCA-negative cHLs.

Description: Abstract 2401 Background. Compelling evidence suggests that chronic infections by various pathogens are linked to lymphoma development. The transformation process is supposed to be either direct (eg for EBV) or indirect. The association between Helicobacter pylori chronic infection and gastric marginal zone lymphoma (MZL) is the best characterized example for an indirect transformation. Several other pathogens such as hepatitis C virus, Campylobacter jejuni or Streptococcus Pneumoniae (Spn) are also suspected to promote B-cell lymphoma development through repeated stimulations of the BCR and/or inflammation. However, except for gastric MZL, animal models are lacking to study potential correlations between chronic infections and lymphoma development. Methods. To amplify and precipitate lymphomagenesis by precluding repair of DNA lesions potentially generated during chronic immune response, p53-deficient mice were used as a permissive model. Given the suspected role of carbohydrates from encapsulated bacteria such as Spn in promoting chronic lymphocytic leukemia, p53−/− (n=15) and p53+/− (n=53) mice were chronically injected with heat-killed Spn until disease development. P53-deficient mice chronically injected with PBS were used as control. Results. Unexpectedly, chronic injections of Spn promoted T-cell rather than B-cell lymphomagenesis in both p53−/− and p53+/− mice and shortened survival in p53+/− mice (P=.004). Whereas mostly thymic CD4+CD8+ double positive T-cell lymphomas have been described in p53-deficient mice, a vast majority of lymphomas observed following chronic Spn injections were of peripheral origin (TdT−) and exhibited an effector memory phenotype (CD44hiCD62LloCCR7−CD25−). Clonality and transferability of those peripheral T-cell lymphomas (PTCL) were established. Furthermore, lymphoma cells showed features of chronically stimulated T cells such as TCR, CD3 or CD4/CD8 co-receptor down-regulations along with PD-1 up-regulation. Several lines of evidence suggested a contribution of the TCR to the development of these PTCL: 1/all PTCL following Spn injections exhibited a Vß repertoire usage bias (Vß8 in 100%) consistent with a transformation process originating from a chronically-stimulated T cell by a pathogen-specific immunodominant peptide; 2/cyclosporin A, a strong TCR signaling inhibitor, decreased cell survival in vitro, and prolonged mice survival following transfer of lymphoma cells into recipient mice; 3/engraftment of CD8+ PTCL in MHC class I KO mice was significantly reduced compared to wild type mice (P450 days) compared to T-cell lymphoma prompted us to dissect the potential role of p53 in mature T-cell response in a context of chronic stimulation. WT and p53−/− negatively selected CD4+ and CD8+ T cells were repeatedly (ie every 7–10 days) stimulated in vitro using anti-CD3/anti-CD28-coated beads. In agreement with previous reports, no significant difference of cell viability was observed after the first or the second stimulation confirming the minor role of p53 in initial activation and proliferation as well as in activation-induced cell death. Nonetheless, a dramatic increase in cell viability was observed 48h after the third stimulation of p53−/− T cells, indicating a crucial function of p53 in deletion of chronically activated T cells. Conclusion. Chronic stimulations with heat-killed Spn unexpectedly increased peripheral T-cell lymphoma development in p53-deficient mice. Phenotypic characterization was consistent with a transformation process occurring in a pathogen-specific chronically-stimulated T cell. The incidence of p53 mutations is higher in T-cell than in B-cell mature malignancies in humans and the p53 pathway is functionally impaired in virtually all enteropathy-associated T-cell lymphomas, which are supposed to be a key model for an antigen-driven process. Therefore, aside from its known role in immature T-cell lymphoma development and in progression of B-cell malignancies, our work sheds light on a previously unsuspected physiopathological role of the p53 pathway in peripheral T-cell lymphomagenesis. Disclosures: No relevant conflicts of interest to declare.

Description: Abstract 2397 B cells can undergo at least two differentiation pathways, dependent of T cells or not, starting from follicular or marginal zone B cells respectively. The T-independent response, less understood than the germinal center reaction, is triggered by specific antigens and arises from marginal zone B cells. During this development, some B cells undergo somatic hypermutation (SHM) and class switch recombination (CSR), triggered by the same DNA editing enzyme called Activation Induced Cytidine Deaminase (AID). The splenic marginal zone lymphoma (SMZL) is a rare lymphoproliferative disorder characterized by a clonal expansion of B cells in the marginal zone of the spleen. These B-cells underwent SHM in roughly 60% of the cases but nearly none underwent CSR. These observations suggest that tumor clones originate from a particular activated B cell subset not transiting through the germinal center. In order to confirm this hypothesis, we focused our work on the status and impact of AID in this disease and worked on purified B cells extracted from spleen of well-characterized SMZL cases. We determined AID status by quantitative RT-PCR analysis on 27 SMZL samples and compared it with 5 controls. In the SMZL group the relative level of expression of AID is heterogeneous but two subgroups could be distinguished: one considered as expressing AID (14 cases out of the 27 analyzed), the remaining considered as not expressing AID. When we compared AID expression rate with occurrence of SHM and CSR, no clear correlation between AID expression and presence of SHM or CSR could be observed suggesting that AID, when expressed, is dysfunctional. To address this hypothesis, we first analyzed AID protein by immunohistochemistry and a good correlation between IHC signal and AID mRNA expression level has been observed. As AID gene was not mutated, we next focused our work on AID mRNA splicing variants as these variants exhibit different functions according to the domain of the protein they contain in a murine model. We found that SMZL B cells express various splicing variants of AID mRNA, some of those variants corresponding to the full length isoform (n = 6/17), and other variants corresponding to AID-ΔE4a (n = 2/17) or AID-ΔE4 (n = 7/17) isoforms known to be expressed in normal germinal center B cells as well as in Chronic Lymphocytic and Acute Lymphoblastic Leukemia. These findings indicate that although expressed at the mRNA and protein levels, AID may not be fully functional in SMZL cases. Finally we addressed the potential clinical significance of AID expression. We identified for that purpose a group of “progressive SMZL” patients that had received immuno-chemotherapy after splenectomy because of a significant risk of progression or transformation into aggressive large B cell lymphoma (n = 8/27) pre-empting outcome differences. We found a higher proportion of AID expressing patients in the defined “progressive SMZL” group (n = 7/8) as compared to the proportion found in the “indolent SMZL” group (n = 5/14, p = 0,03). Altogether, this data suggest that the B cell clone leading to SMZL originate from the marginal zone and support the hypothesis of a lymphoproliferative disorder affecting the T-independent response. AID expression in SMZL may reflect an advanced stage of the disease and could be correlated with the evolution of the lymphoma into a more clinically or pathologically aggressive form. Disclosures: No relevant conflicts of interest to declare.